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Bacterial Testing of Contact Lens Solutions
VOL. 64, NO. 3
CORRESPONDENCE
OBTAINING DONOR EYES
Editor, American Journal of Ophthalmology : What finer way to reward an intern who has obtained permission from the relatives of a deceased patient to donate the eyes to the nearest eye-bank, than to give him the opportunity to remove the eyes under super vision of an ophthalmologist? Internes get little practice in surgery and no practice in eye surgery. This would be a start. An an nual lecture on enucleation, too, would alert internes to the great need for donor eyes. Jerome M. Wolff Plainfield, New Jersey BACTERIAL TESTING OF CONTACT LENS SOLUTIONS
Editor, American Journal of Ophthalmology :
485
Inadequate attention to these variables could result in 1:8 dilution of the organism, or less. If the lid of the test case was not closed, then how was the lens and solution protected from random contamination? A more important consideration, omitted in this paper, is the well-known pellicle for mation, which is a common characteristic of an actively growing Pseudomonas aeruginosa. This will cause some lenses to have large clumps of bacteria clinging to their surfaces. Therefore, the inoculum the author used un doubtedly varied from one lens to the next by several log numbers. Apparently ho at tempt was made to allow or correct for this. The B H I medium was used for both growth of original inoculum and subcul tures. This medium contains phospholipids, including lecithins, cephalins and sphingomyelin, which are well known to inactivate quaternaries. 3 · 4 Most laboratories evaluating quaternaries have employed such agents as inactivators to prevent false negatives. In this study, when the inoculum was added to test solutions containing benzalkonium chlo ride, this antibacterial agent was inactivated instantly, causing it to appear ineffective. It is illogical to test antibacterial activity in the presence of an inactivating agent. The au thor has unknowingly demonstrated a wellknown fact: that certain anionic materials activate quaternaries.
Recently, your journal published an arti cle, "Bacterial decontamination of contact lenses," by Donald P. Bixler, M.D. (Am. J. Ophth. 62:324, 1966). The test procedures the author used leave his conclusions open to serious criticism. Being concerned for years with the anti-Pseudomonal activity of preservatives proposed for ophthalmic solu tions,1'2 I feel obligated to comment on this paper. In this study, the author used several Test contact lenses were inoculated by pouring a culture of Pseudomonas aerugino- fluids of varying viscosities, ranging from sa (age not given), grown in brain heart in watery to very viscous. Therefore, without fusion ( B H I ) over the lenses. Such cul either recognizing or correcting for these tures, 18-24 hours old, usually contain variations, all lenses were transferred in 10M0 10 organisms per ml. The contaminat similar manner to BHI medium. In some ed lenses were transferred to sterile lens instances there was probably a large carry cases and covered with 0.5 ml of a variety over of the antibacterial agents into the sub of test solutions. In reviewing this proce culture medium. No evidence was presented to prove that BHI would inactivate the rela dure, it was found: 1. That 0.01-0.06 ml of the culture me tively large amounts of antibacterial agents, dium stuck to the lens (depending on whether such as merthiolate, transferred in this way. For example, one solution observed to be the lens was shaken or not). 2. With cases such as were described, most effective was also the most viscous. It is well known 5 · 8 that inactivation of or normally 0.1-0.2 ml of test solution was lost from the 0.5 ml added, if the lid was closed. ganic mercurials is most difficult and re-
486
AMERICAN JOURNAL OF OPHTHALMOLOGY
quires the use of sulfhydril-containing com pounds, that is, thioglycollate, and adequate dilution. Critical tests done on BHI medium indicate that it does not possess inactivating activity for mercurials. Inoculum of a known number of Pseudomonas aeruginosa organisms (pour plate counts at zero, one hour through six hours, and at 24 and 48 hours) into a mixture of BHI medium con taining 1:100,000 merthiolate decreased pro gressively during the test period. Viable or ganisms were recovered at all times, in cluding the 48-hour count. This corresponds to the author's observation period. The re sults might have been different if the author had done even a second subculture to intro duce a dilution factor. A careful examination of the author's procedure indicates that the lens merely served as a way of transferring a variable and excessively large number of organisms into an antibacterial solution. There is abun dant scientific literature establishing proof of the rapid Pseudomonicidal activities of quaternaries, when evaluated by appropriate techniques.7·8 Contrary to the author's findings, there is literature reporting the slow killing rate of mercurials.3'4 Organic mercurials and quaternary pre servatives have been shown equally to lose activity or to be completely inactivated by chemical or physical treatments, that is, well-known light instability of thimerosal. Well-formulated contact lens solutions, con taining benzalkonium chloride or other qua ternaries, used according to manufacturers' instructions, are among the most effective and rapidly acting Pseudomonicidal agents known. When these agents have failed, it has been due, invariably, to unfavorable conditions which inactivate them, such as use of contact lens carrying cases with sponges. Sponge material, like other fibers, adsorbs the quaternary and thereby prevents its protective action." Another unexplained aspect of the paper is the statement by the author that the tap water of Anderson, Indiana, used to rinse
SEPTEMBER, 1967
lenses was repeatedly found to be sterile. This is contrary to Public Health Standards for the United States.10 It should be apparent from these com ments that the conclusions reported by the author are not valid. Sidney Riegelman San Francisco, California REFERENCES
1. Riegelman, S., Vaughan, D. G. Jr. and Okumoto, M. Antibacterial agents in Pseudomonas aeru ginosa contaminated opthalmic solutions. J. Am. Pharm. A. Sei. Ed. 45:93, 1956. 2. Riegelman, S. and Vaughan, D. G. Jr. : A ra tional basis for the preparation of opthalmic solu tions. Survey Ophth. 3:471, 1958. 3. A new medium for study of quaternary bactéricides. Soap & Sanitary Chem. 23:119, 1947. 4. Lawrence, C. A. : Inactivation of the germicidal action of quaternary ammonium compounds. J. Am. Pharm. A. Sei. Ed. 37:57, 1948. 5. Klarmann, E. G. : The role of antagonisms in the evaluation of antiseptics. Ann. N.Y. Acad. Sei. 53:123, 1950. 6. Cook, A. M., and Steel, K. J. : The antago nism of the antibacterial action of mercury com pounds : Part V. Quantitative aspects of the anta gonism of the antibacterial action of mercuric chlo ride. J. Pharm. Pharmacol. 12:219, 1960. 7. Lawrence, C. A. : An evaluation of chemical preservatives for opthalmic solutions. J. Am. Pharm, A. 44:457, 1955. 8. Kohn, S. R., Gershenfeld, L. and Barr, M. Effectiveness of antibacterial agents presently em ployed in opthalmic preparations as preservatives against Pseudomonas aeruginosa. J. Pharm. Sei. 10:967, 1963. 9. Myers, G. E. and Lefebvre, C. : Antibacterial activity of benzalkonium chloride in the presence of cotton and nylon fibres. Canad. Pharm. J. 94:55, 1961. 10. American Public Health A. : Standard meth ods for the examination of water and wastewater, including bottom sediments and sludges. New York, 1960, ed. 11.
BOOK REVIEWS REPAIR AND RECONSTRUCTION OF THE ORBI
By John Clark Mustarde. Baltimore, Williams and Wilkins Com pany, 1966. Clothbound, 382 pages, 324 fig ures in black and white, 4 figures in color, index. Price: $18.50 Rapid expansion of many branches of surgery has inevitably produced the need TAL REGION.
CORRESPONDENCE
OBTAINING DONOR EYES
Editor, American Journal of Ophthalmology : What finer way to reward an intern who has obtained permission from the relatives of a deceased patient to donate the eyes to the nearest eye-bank, than to give him the opportunity to remove the eyes under super vision of an ophthalmologist? Internes get little practice in surgery and no practice in eye surgery. This would be a start. An an nual lecture on enucleation, too, would alert internes to the great need for donor eyes. Jerome M. Wolff Plainfield, New Jersey BACTERIAL TESTING OF CONTACT LENS SOLUTIONS
Editor, American Journal of Ophthalmology :
485
Inadequate attention to these variables could result in 1:8 dilution of the organism, or less. If the lid of the test case was not closed, then how was the lens and solution protected from random contamination? A more important consideration, omitted in this paper, is the well-known pellicle for mation, which is a common characteristic of an actively growing Pseudomonas aeruginosa. This will cause some lenses to have large clumps of bacteria clinging to their surfaces. Therefore, the inoculum the author used un doubtedly varied from one lens to the next by several log numbers. Apparently ho at tempt was made to allow or correct for this. The B H I medium was used for both growth of original inoculum and subcul tures. This medium contains phospholipids, including lecithins, cephalins and sphingomyelin, which are well known to inactivate quaternaries. 3 · 4 Most laboratories evaluating quaternaries have employed such agents as inactivators to prevent false negatives. In this study, when the inoculum was added to test solutions containing benzalkonium chlo ride, this antibacterial agent was inactivated instantly, causing it to appear ineffective. It is illogical to test antibacterial activity in the presence of an inactivating agent. The au thor has unknowingly demonstrated a wellknown fact: that certain anionic materials activate quaternaries.
Recently, your journal published an arti cle, "Bacterial decontamination of contact lenses," by Donald P. Bixler, M.D. (Am. J. Ophth. 62:324, 1966). The test procedures the author used leave his conclusions open to serious criticism. Being concerned for years with the anti-Pseudomonal activity of preservatives proposed for ophthalmic solu tions,1'2 I feel obligated to comment on this paper. In this study, the author used several Test contact lenses were inoculated by pouring a culture of Pseudomonas aerugino- fluids of varying viscosities, ranging from sa (age not given), grown in brain heart in watery to very viscous. Therefore, without fusion ( B H I ) over the lenses. Such cul either recognizing or correcting for these tures, 18-24 hours old, usually contain variations, all lenses were transferred in 10M0 10 organisms per ml. The contaminat similar manner to BHI medium. In some ed lenses were transferred to sterile lens instances there was probably a large carry cases and covered with 0.5 ml of a variety over of the antibacterial agents into the sub of test solutions. In reviewing this proce culture medium. No evidence was presented to prove that BHI would inactivate the rela dure, it was found: 1. That 0.01-0.06 ml of the culture me tively large amounts of antibacterial agents, dium stuck to the lens (depending on whether such as merthiolate, transferred in this way. For example, one solution observed to be the lens was shaken or not). 2. With cases such as were described, most effective was also the most viscous. It is well known 5 · 8 that inactivation of or normally 0.1-0.2 ml of test solution was lost from the 0.5 ml added, if the lid was closed. ganic mercurials is most difficult and re-
486
AMERICAN JOURNAL OF OPHTHALMOLOGY
quires the use of sulfhydril-containing com pounds, that is, thioglycollate, and adequate dilution. Critical tests done on BHI medium indicate that it does not possess inactivating activity for mercurials. Inoculum of a known number of Pseudomonas aeruginosa organisms (pour plate counts at zero, one hour through six hours, and at 24 and 48 hours) into a mixture of BHI medium con taining 1:100,000 merthiolate decreased pro gressively during the test period. Viable or ganisms were recovered at all times, in cluding the 48-hour count. This corresponds to the author's observation period. The re sults might have been different if the author had done even a second subculture to intro duce a dilution factor. A careful examination of the author's procedure indicates that the lens merely served as a way of transferring a variable and excessively large number of organisms into an antibacterial solution. There is abun dant scientific literature establishing proof of the rapid Pseudomonicidal activities of quaternaries, when evaluated by appropriate techniques.7·8 Contrary to the author's findings, there is literature reporting the slow killing rate of mercurials.3'4 Organic mercurials and quaternary pre servatives have been shown equally to lose activity or to be completely inactivated by chemical or physical treatments, that is, well-known light instability of thimerosal. Well-formulated contact lens solutions, con taining benzalkonium chloride or other qua ternaries, used according to manufacturers' instructions, are among the most effective and rapidly acting Pseudomonicidal agents known. When these agents have failed, it has been due, invariably, to unfavorable conditions which inactivate them, such as use of contact lens carrying cases with sponges. Sponge material, like other fibers, adsorbs the quaternary and thereby prevents its protective action." Another unexplained aspect of the paper is the statement by the author that the tap water of Anderson, Indiana, used to rinse
SEPTEMBER, 1967
lenses was repeatedly found to be sterile. This is contrary to Public Health Standards for the United States.10 It should be apparent from these com ments that the conclusions reported by the author are not valid. Sidney Riegelman San Francisco, California REFERENCES
1. Riegelman, S., Vaughan, D. G. Jr. and Okumoto, M. Antibacterial agents in Pseudomonas aeru ginosa contaminated opthalmic solutions. J. Am. Pharm. A. Sei. Ed. 45:93, 1956. 2. Riegelman, S. and Vaughan, D. G. Jr. : A ra tional basis for the preparation of opthalmic solu tions. Survey Ophth. 3:471, 1958. 3. A new medium for study of quaternary bactéricides. Soap & Sanitary Chem. 23:119, 1947. 4. Lawrence, C. A. : Inactivation of the germicidal action of quaternary ammonium compounds. J. Am. Pharm. A. Sei. Ed. 37:57, 1948. 5. Klarmann, E. G. : The role of antagonisms in the evaluation of antiseptics. Ann. N.Y. Acad. Sei. 53:123, 1950. 6. Cook, A. M., and Steel, K. J. : The antago nism of the antibacterial action of mercury com pounds : Part V. Quantitative aspects of the anta gonism of the antibacterial action of mercuric chlo ride. J. Pharm. Pharmacol. 12:219, 1960. 7. Lawrence, C. A. : An evaluation of chemical preservatives for opthalmic solutions. J. Am. Pharm, A. 44:457, 1955. 8. Kohn, S. R., Gershenfeld, L. and Barr, M. Effectiveness of antibacterial agents presently em ployed in opthalmic preparations as preservatives against Pseudomonas aeruginosa. J. Pharm. Sei. 10:967, 1963. 9. Myers, G. E. and Lefebvre, C. : Antibacterial activity of benzalkonium chloride in the presence of cotton and nylon fibres. Canad. Pharm. J. 94:55, 1961. 10. American Public Health A. : Standard meth ods for the examination of water and wastewater, including bottom sediments and sludges. New York, 1960, ed. 11.
BOOK REVIEWS REPAIR AND RECONSTRUCTION OF THE ORBI
By John Clark Mustarde. Baltimore, Williams and Wilkins Com pany, 1966. Clothbound, 382 pages, 324 fig ures in black and white, 4 figures in color, index. Price: $18.50 Rapid expansion of many branches of surgery has inevitably produced the need TAL REGION.